Perioperative plasma melatonin concentration in postoperative critically ill patients: its association with delirium.

PURPOSE Delirium is a common complication in postoperative critically ill patients. Although abnormal melatonin metabolism is thought to be one of the mechanisms of delirium, there have been few studies in which the association between alteration of perioperative plasma melatonin concentration and postoperative delirium was assessed. MATERIALS We conducted a prospective observational study to assess the association of perioperative alteration of plasma melatonin concentration with delirium in 40 postoperative patients who required intensive care for more than 48 hours. We diagnosed postoperative delirium using Confusion Assessment Method for the intensive care unit and measured melatonin concentration 4 times (before the operation as the preoperative value, 1 hour after the operation, postoperative day 1, and postoperative day 2). RESULTS Postoperative delirium occurred in 13 (33%) of the patients. Although there was no significant difference in preoperative melatonin concentration, Δ melatonin concentration at 1 hour after the operation was significantly lower in patients with delirium than in those without delirium (-1.1 vs 0 pg/mL, P = .036). After adjustment of relevant confounders, Δ melatonin concentration was independently associated with risk of delirium (odds ratio, 0.50; P = .047). CONCLUSIONS Delta melatonin concentration at 1 hour after the operation has a significant independent association with risk of postoperative delirium.